I have the Martin 0XK and LOVE IT!
It is very responsive to DYNAMICS, as in if you play softly, it has a sweet tone, and if you really drive the strings with some hard strumming it has some bark and bite, as well as great sustain in any level of volume.
Out of the box I'm not sure since I got my used, but the seller said that no setup work was done or needed, and my unit has great action and very good intonation, only rivaled by my Fluke and Flea ukes.
One point of interest is that the saddle is compensated in a way that uniquely takes advantage of the Martin M600 strings to provide better intonation. The Martin strings have a 0.034" fluoro C string, which is thicker diameter than nearly every other of the more than 100 sets of strings I've tried. The saddle on the 0XK has the C string angled TOWARDS the nut, whereas on most other ukes with pre-compensated saddles, the C string is angled AWAY from the nut.
I have tried other strings on this instrument, Worths CL, CM, BL, BM, Fremont Blacklines, and Oasis both 'brite' and 'warm' high-G and all had intonation problems on the C string, so since I was not interested in changing the saddle right now, AND since the Martin strings are usually my preferred, I have been using the M600s now thru 2 string changes after the stock ones wore out.
I also tried Aquila New Nylgut, as well as SuperNylgut and was not happy with them at all on this intrument.
The weight is pretty light to me (I am usually a tenor player), and I always use a strap, even on this uke. I also changed out the original friction tuners (which all friction tuners are an anathema to me) to the Gotoh UPT-L planetary geared tuners and am very happy with the balance and weight, which is to say, that I dont think about it, but if you do not want to use a strap, your feelings might differ...
If you change to the Gotoh, you will need the UPT-
L and NOT the 'plain' UPT model, the '
L' stands for 'LONG SHAFT'. The 'plain' UPT model will not fit on the thickness of the headstock.
Even though this instrument is made of a formica-like material, it sounds as good or better than some of my other ukes, and has quenched my UAS for a good soprano.
Budget permitting, I'd buy a second one, maybe in the bamboo 'natural' color, and on that one
change the saddle since I'd want to use it for GDAE (mandolin) fifths tuning, and with these strings, you have 2 wounds and compensation is different when compared to all non-wound strings, otherwise the intonation is all over the place from string-to-string...
Hope this helps!